The invention is directed to a control method for regulation of the magnets of a magnetically levitated railroad, with the use of at least three variables, which are acquired in an observer unit (support circuit) based on the measured magnitudes for the magnet gap width s as well as the magnet acceleration b, as well as an associated control unit.
Such a method is known from the DE-Al 35 01 487. There a control loop for a magnetically levitated vehicle is described, which is guided along a track by controlled support- and guidance magnets. The control loop comprises an observer unit designated as a support circuit or support loop, which is fed by the magnet acceleration b in the direction of the magnetic attraction force, as well as the magnet gap width s by way of measured magnitudes. The support loop forms three variable magnitudes in the form of estimated values for the magnet gap width, the gap change velocity as well as the magnet acceleration with the help of summation or adding links, integrators and amplifier links. Theseestimated values are respectively fed to an amplifier or gain link, whose three output values are fed to an additional summation member, from which finally the control unit output signal can be derived. In general, such control loops are used in order to enable a stable levitation of the magnetic vehicle during standstill and a good following behavior at all traveling speeds. In the voltage control method described in the DE-Al 35 01 487 it is essentially intended to maintain the stability of the vehicle in a simple manner also when levitating at standstill. It is provided there for that reason to assign an adaptive rail observation unit to each support magnet, which is matched to the track vibrations, and which generates an adaptive signal, which is superimposed to the control loop of the same support magnet.
A control loop for an magnet elastically suspended at the levitating chassis--a magnetic wheel--has the form depicted in FIG. 1: herein the symbols mean:
v: traveling speed PA1 b=z (z: magnet coordinate) PA1 s=z--h (h: rail coordinate) PA1 s.sub.o : required magnet gap PA1 h and z are defined with respect to a fictitious inertial guide or pilot line.
The control unit utilizes signals which are measured directly at the location of the magnet, this being the object to be control. In order to assure the stability of a magnetic wheel in the course of voltage control, three variables have to be fed back. These are for instance the values s, s' and b=z. Since s' cannot be directly measured, this value is at least determined as an estimated value s from a reduced observer unit. Since the set of the three state variables thus obtained does not yet assure a sufficient following behavior, it is desirable to design the observer unit in such a way that it also supplies an approximate s.apprxeq.s.
The derivation of s or s from s and z is always connected with a differentiation of the rail coordinate. Thus, for example, s can be represented in Laplace presentation by an observer of the first order as ##EQU1##
Thus in limiting cases there applies: ##EQU2##
An improvement of the differentation (smaller .tau.) yields thus a high noise component because of high frequency rail disturbances, which must no longer be followed. This noise component can lead to instabilities because of the natural limits of the actuator. In case of a real guideway, which must be economical because of reasons of cost, there will thus always exist tolerances, which result in a high background noise component. From (1) one recognizes further that one does not have a following system or follow-up for the rail h.sub.(f), rather for the rail contour ##EQU3##
Even in case of a hard coupling to h there result thus changes in the gap because of the phase between h and h.
It follows from the above explanations that the rail tolerances permit only a minimum value of .tau. and thus a limited estimation of h, with this however they determine the optimum following or follow-up behaviour and with this the required air gap.